Method of producing brake drums



April 10, 1934. c, w D Q 1,954,665

METHOD OF PRODUCING BRAKE DRUMS Filed July 25, 1932 2 Sheets-Sheet l 3 I Y I i //1' Z4 u n W g f M 5g 2 Y Q 16 mm z I V I? Charles Mkhgfig I 7 .1 3 v3Q g l8 M f 25 9 ATYomeq April 10, 1934. C, w, DAKE 1,954,665

METHOD OF PRODUCING BRAKE DRUMS Filed July 25, 1932 2 Sheets-Sheet 2 ii! I Chimes Patented Apr. 10, 1934 1 UNITED STATES PATENT {OFFICE METHOD or PRODUCING BRAKE DRUMS Charles W. Dake, Grand Haven, Mich., assignor to Campbell, Wyant & Cannon Foundry Company, Muskegon Heights, Mich., a corporation of Michigan Application July 25, 1932, Sierial No. 624,606 2 Claims. (Cl. 29--152.2)

This invention relates to the method of promay be driven through any suitable power drivducing brake drums for motor vehicles and the ing mechanism connected to the gear 5 which is like, and is primarily concerned with a drum in fixed on the spindle, and the stopping the rotawhich the outer supporting portion thereof has tion may be controlled and made more rapid by 5 the characteristics of mild steel for required utilizing a brake 6 associated with said spindle. C9

strength and toughness, and the inner portion of An upwardly and outwardly extending surthe drum against which brake shoes or the like rounding ring 7 is connected and locked to the pe- Will act in practice has the high braking characripheral portions'of the table 1 by a spring ring teristics of cast iron, the drum being in effect an 8 as shown and within the said ring or flange '7 a integral composite structure formed integrally sectional composite mold is located. Such mold 65 as to its casting in one operation, and being later comprises a horizontal base 10 above and around treated by a process like that used for the producthe outer portions of which are segmental ring tion of malleable ironto obtain an outer relativemembers 11 and 12 located one over the other; and iv tough supporting portion of high tensile above the upper segmental ring 12 is a circular strength, and finished at its inner side to present a plate 13 having a central opening 14 as shown. It braking surface having the braking characteriswill be noted that at the junctures of the outer tics of cast iron. I portion of the base 10 of the mold and the seg-' The present invention is directed to a novel mental ring portion 12 of the mold above the method for producing such drum and to the prodsame, there is provided a continuous annular uct obtained thereby whereby a drum of inconsidgroove and, likewise, between the segmental rings 75 erable weight and not greater than is thoroughly 11 and 12 and between the upper ring 12 and the practical for automobile use is produced, and one upper plate 13 such annular grooves are prowhich will not be readily fractured under the vided. shocks and stresses to which it is subjected in A central core 15, located within the surroundservice. 7 ing ring members 11 and 12, rests upon the base These objects and others not at this time spe- 10 and is covered by the circular plate 13. The cifically enumerated will be apparent as undercore 15 is of cylindrical form and has a central standing of the invention is had from the followconical opening 16 therein as shown, while at the ing description, taken in connection with the lower side of the core a plurality of gate passages 30 accompanying drawings, in which, 17 are made separated by supporting feet 18 be- Fig. 1 is a central vertical section on the plane tween the passages and integral with the core. of line 1-1 of Fig. 3, of one form of apparatus These parts, when assembled, constitute a mold by means of 'which I am able to carry out the and the parts thereof are held securely in place process and produce the initial drum. y a n 1 m d p Of a plurality of Segments,

35 Fig. 2 is a similar fragmentary section illusthe peripheral edges of which are inclined outtrating a slight modification in the apparatus. wardly to fit underneath the overhanging lips 9 Fig. 3 is a horizontal section on the plane of at the upper edges of the surrounding ring 7 servline 3-3 of Fig. 1 looking upwardly. ing to lock and hold the parts of the mold in Fig. 4 is a reduced horizontal section on th position.

40 plane of line 4-4 of Fig. 1 looking upwardly, and The core at its peripheral surface is spaced a Fig. 5 is a fragmentary enlarged section illusshort distance from the inner curved sides of the trating the machine operation performed at the rings 11 and 12 and at its lower side and outer inner side of the drum after it has been subjected portions is space m the upper Side Of t b tto the malleablizing process, whereby the inner tom 10 making a mold cavity as shown;

45 surface portionsof the drum is cut away and the the s t y modified form Shown in 130 surface finished to present a braking'surface havthe base does not extend to the inner side of ing the braking characteristics of castiron. the surrounding ring 7, and the sides of the mold Like reference characters refer to like parts in instead of being made up of a plurality of rings the different figures of the drawings. 11, 12 are provided in a single ring 21 grooved 50 The apparatus disclosed is a centrifugal moldat its irmer side; and the same may be exteriorly ing device having a horizontal table 1 secured covered by a thin sheet metal covering 22 as at the upper end of a vertical spindle 2 which is shown in Fig. 2. The mold in either case, howrotatably mounted to turn about its longitudinal ever, is in effect the same. vertical axis in anti-friction bearings 3 suitably Melted cast iron suitably alloyed, or melted cast 55 mounted on a. support 4. The vertical spindle 2 steel is poured through the opening at 14 into the mold coming against the upper side of the bottom 10 of the mold, and with the mold rapidly rotating, the melted iron, through centrifugal force and action, is carried through the gate passages 17 to the cavities of the mold and rises in the mold to completely fill all interstices thereof, thereby providing a cast drum 23 of cylindrical form, having continuous annular outwardly extending ribs 24 thereon, and with an inwardly extending s'upporting flange 25 to which, after the cast drum has been further treated in accordance with my process, a suitable back of wrought metal is secured as by welding or other equivalent permanent connection to complete the brake drum.

The cast drum 23, with its outwardly extending ribs 24 and inwardly extending flange 25, after it has been cast and has been removed from the mold, which is of separable parts, is subjected to the process ordinarily employed in the manufacture of malleable iron, whereby all exposedsurfaces of the'drum and the metal for a limited distance inwardly therefrom is changed in its properties and characteristics to have the properties and characteristics of a mild steel, with increased tensile strength and with greater toughness and an ability to withstand shocks, the readily breakable, or brittle characteristics of cast iron, insofar as the exposed surface portions of the drum are concerned, being eliminated.

In Fig. 5 is an illustration of a cross section of the drum after it has been subjected to the malleable process, and is being subjected to the final step of the process. The inner core of the drum, indicated at 26, retains the characteristics of the cast metal from which the drum was made, while the outer and inner portions 27 and 28 of the drum have been changed to characteristics and properties similar to those of mild steel as described. v

The-final step of the process is to machine the inner part 28 of the drum in a lathe or other suitable apparatus, cutting the scale and so much of the drum away as will expose the harder core 26, the tool 29 shown being a conventional showing of a cutting tool used on lathes or the like.

The removal ofthe inner portion or surface to a depth sufficient to expose the core or body having the desired cast iron characteristic provides a a brake drum with the toughness strength and other characteristics of steel for the surrounding outer portion of the drum, and with a braking surface thcharacteristics of which may be varied by varying the different alloying elements which may be used in the cast iron mixture forming the brake drum, thereby'producing a brake drum hav-' ing desired strength and light weight and the very desirable cast iron braking surface at the inner side of the drum.

In the cast iron composition used, preferably, the main element of course is iron, but in all cast iron thereare certain percentages of carbon and nearly always of silicon; and there may be small percentages of othere'lements in the cast iron such as phosphorus, sulphur, man'- ganese, chromium or equivalents. Preferably the composition which I make use of shall not have less than 2 percent by weight of carbon nor more than 3.4 percent of carbon; and with respect to silicon, not more than 1.3 percent nor less than /4 of one percent by weight of silicon. The other elements which may be present in the castdron are of little importance except that of doursekulphur and phosphorus, not being desirable eleinents, will be kept to a minimum as much as possiblefr The carbon element is necessary for the purpose of annealing the cast iron and its'conversion into so-called malleable iron while silicon, as is well known to workers in cast iron, has desirable qualities in increasing the fluidity of the melted iron and softening the same whereby the central core, which is exposed by cutting away the inner side of the drum at 28, as illustrated in Fig. 5, is of a uniform texture throughout the braking surface and should change somewhat as the drum wears, it will be substantially uniform at all exposed wearing points.

While I have described the drum as having been made from cast iron it is to be understood that there are certain steels which will produce a drum similar to that shown in Fig. 5 and which will have a harder core at the inner portions of the drum flange and tougher and stronger surrounding surface portions; and that a drum made of cast steel may have the annealing process used in the manufacture of malleable iron dispensed with and may be finished by removing the inner surface of the cast steel drum to expose the core of different characteristic. And my invention is to be considered as comprehending the brake drum produced whether cast iron followed by a malleable iron annealing process is used, or cast steel wherein the solidification of steel drum produces a core of different characteristics than the surface portions.

Having fully described the invention, what I claim and desire to secure by Letters Patent is:

1. The herein described process of producing brake drums which consists in casting a brake drum of cast iron, subjecting the same to a malleabli zing process for a limited time whereby the same has its characteristics changed to a predetermined depth, and then removing a portion at a chosen side of the drum flange, said portion being of such depth as to uncover the substantially unchanged original cast metal, thereby exposing a braking surface having the characteristics of cast iron and leaving an adjacent surrounding inte ral portion on the drum of tougher characteristics and having a higher tensile strength than the braking portion.

2. The herein described process of producing a brake drum which consists, in centrifugally casting a drum from molten iron to provide a cast iron drum, annealing said drum by subjecting the same to malleablizing process for a limited time, and removing the inner surface portions of the drum flange sufliciently to remove the annealed shell and to expose the harder inner body to provide an inner core having substantially the characteristics and properties of cast .iron, said core being surrounded and integral with an outer portion having substantially the characteristics of mild steel.

CHARLES w. DAKE. 

